This application is aimed at elucidation of certain conformational and mechanistic aspects of glycoprotein hormones, polypeptide hormones, and opioid peptides. We propose to study physicochemical properties of the gonadotropins, lutropin (LH), choriogonadotropin (HCG), subunits, recombinants and fragments, using a variety of techniques, including circular dichroism, electron paramagnetic resonance, and nuclear magnetic resonance. Mechanism-of-action studies on LH and HCG will be conducted using Leydig cells and Leydig tumor cells in a perifusion system. Investigations will be made on the opioid peptide-receptor interaction using brain membranes and cultured neuroblastoma cells. Other chemical and biological studies will be conducted on pituitary-derived growth factors and corticotropin.